There the two large nuts that hold the bar on … and there’s a smaller screw and nut for adjusting tension, and this nut has a bit of a flange on it … that flange has to insert into the hole in the bar … so that as we turn the screw, that flanged nut will push or pull the bar in or out …
A little late for the OP but still a good resource.
Poulan Pro Chainsaw manuals. And thousands of other manuals as well.